How to install RAM in pairs so that it will run in dual chanel?

I have 1gb ddr2 667Mhz PC2-5300 installed currently and i bought another one identical.
As you can see my motherboard has 4 slots with 2 colours, in which slot should i put them so that they will work in dual chanel?

Sorry but we cannot see your motherboard. But I expect your 4 RAM slots have have alternate colours, on mine they are Blue Black Blue Black coming from the CPU/Heatsink. You want to put the RAM in the two blue slots (first and third).

If you can post the make/model of motherboard we will be able to confirm the colours of RAM slots.